Firm, low smear, skin pH or weakly acidic cleansing bars as defined herein, are believed to be novel. U.S. Pat. No. 3,557,006, Ferrara et al., issued Jan. 19, 1971, discloses a composite soap bar having an acid pH in use. Also see U.K. Pat. Specification 513,696, Mangeot, accepted Oct. 19, 1939. Jap. Pat. Application. No. 54-151410, filed Nov. 21, 1979, and published Jun. 6, 1985, discloses a weakly acidic cleansing cream, but useful solids are not disclosed. A "weakly acidic" bar has a pH of from about 4.8 to about 6 which is distinguished from a neutral pH bar.
Commercial neutral pH bars, e.g., DOVE.RTM., CARESS.RTM., and OLAY .RTM., usually contain only a maximum of about 5% moisture. Prior art neutral pH bars containing substantial levels of hygroscopic materials, soft solids, or liquids, including water, are soft or sticky with poor smears; such prior art neutral pH bars are soft or have relatively poor smears.
Cleansing bars, per se, with reduced bar smear are reported in the art. E.g., U.S. Pat. No. 2,988,511, Mills, issued Jun. 13, 1961, incorporated herein by reference, discloses a low smearing bar.
Bar smear, also referred to as bar sloth, is the soft solid or mush that forms at the surface of a bar when submerged in water and is regarded by consumers as messy, unattractive, and uneconomical.
High moisture and low smear personal cleansing bars are disclosed in U.S. Pat. No. 4,606,839 Harding, issued Aug. 19, 1986. Harding uses coconut and/or palm kernel oil soap.
However, an examination of a used personal cleansing bars in today's average bathroom will show that there is still a need to improve cleansing bar smear.
Bar smear is especially poor in neutral pH bar formulations which contain higher levels (50%.+-.10%) of synthetic surfactant.
The formation of rigid, soap curd fibers of sodium laurate is reported by L. Marton et al. in a 1940 Journal of American Chemical Society (Vol. 63, pp. 1990-1993). The report does not teach a utility for the soap curd. Shaped solids, as defined herein, are not disclosed by Marton et al. Additionally, the formation of this curd of fibers does not disclose free mono- and/or dicarboxylic acids.
Japanese Pat. J5 7030-798, Jul. 30, 1980, discloses transparent solid framed or molded soap bar in which fatty acids constituting the soap component are myristic, palmitic, and stearic acids. A transparent soap is described in which at least 90 wt.% of the fatty acids which constitute the soap component are myristic acid, palmitic acid, and stearic acid. The product is reported as a transparent, solid soap having good frothing and solidifying properties, good storage stability, and a low irritant effect on human skin. The process and transparent bar soap composition exemplified in Jap. J5 7030-798 do not appear to contain synthetic surfactant.
It is an object of the present invention to produce a firm, mild, skin pH, low smear cleansing bar that contains relatively high level of moisture in the presence of a synthetic surfactant and soft solids, such as water-soluble polyols and hydrocarbon greases.